Infants up to 12 months need 400 IU (10 mcg) of vitamin D daily, and children ages 1 through 18 need 600 IU (15 mcg) daily. These recommendations, set by the National Academies of Sciences, Engineering, and Medicine, apply equally to boys and girls at every age.
Daily Intake by Age Group
The recommended amounts break down into two tiers. Babies in their first year have a lower target because of their smaller body size, while every child from toddlerhood through the teen years shares the same number:
- 0 to 12 months: 400 IU (10 mcg)
- 1 to 3 years: 600 IU (15 mcg)
- 4 to 8 years: 600 IU (15 mcg)
- 9 to 13 years: 600 IU (15 mcg)
- 14 to 18 years: 600 IU (15 mcg)
The infant recommendation is technically classified as an “Adequate Intake” rather than a full RDA, because there isn’t enough data from controlled trials in babies to set a firm requirement. In practice, 400 IU is the number pediatricians use.
Why Breastfed Babies Need a Supplement
Breast milk is low in vitamin D, typically providing only 25 to 50 IU per liter. That’s nowhere near the 400 IU a baby needs. The CDC recommends that all babies who are exclusively breastfed, or who get a mix of breast milk and formula, start a liquid vitamin D supplement of 400 IU per day shortly after birth. Babies who drink at least 32 ounces of vitamin D-fortified formula daily generally get enough without a separate supplement, but most newborns aren’t consuming that volume right away.
Liquid vitamin D drops designed for infants typically deliver exactly 400 IU in a single drop, making dosing straightforward. You can place the drop directly on a nipple or pacifier, or mix it into a small amount of expressed milk.
Why Vitamin D Matters for Growing Bones
Vitamin D’s primary job in children is helping the body absorb calcium from food. When vitamin D levels are adequate, the intestines absorb 30 to 40 percent of the calcium passing through. When levels drop too low, that absorption rate falls to just 10 to 15 percent. No matter how much calcium-rich food your child eats, their body can’t use it efficiently without enough vitamin D.
When blood levels of vitamin D stay low for a prolonged period, the body compensates by pulling calcium out of bones to keep blood calcium stable. Over time this weakens the skeleton. In children, this process can eventually lead to rickets, a condition where bones become soft and bend under the body’s weight. Rickets causes bowed legs, incorrect growth patterns, joint deformities, bone pain, and muscle weakness. Even mild deficiency, well short of rickets, can leave kids with sore or weak muscles.
Kids at Higher Risk for Deficiency
Some children are more likely to fall short on vitamin D than others. The most common risk factors include:
- Darker skin: Higher melanin levels block more UV light, so the skin produces less vitamin D from the same amount of sun exposure.
- Exclusive breastfeeding without supplementation: As noted above, breast milk alone doesn’t supply enough.
- Limited sun exposure: Kids who spend most of their time indoors, live at northern latitudes, or consistently wear sunscreen or covering clothing synthesize less vitamin D in their skin.
- Obesity: Vitamin D is fat-soluble, and excess body fat sequesters it, making less available in the bloodstream.
- Conditions causing malabsorption: Celiac disease, inflammatory bowel disease, and other gut conditions reduce the body’s ability to absorb vitamin D from food.
- Maternal deficiency: Babies born to mothers with low vitamin D often start life with low stores themselves.
How Much Sun Exposure Helps
Sunlight triggers vitamin D production in the skin, but the amount you get varies enormously based on where you live, the season, the time of day, and your child’s skin tone. Research conducted at the latitude of Kansas City, Missouri found that a person with lighter skin and about 25 percent of their body exposed (hands, face, neck, and arms) needed roughly 8 to 10 minutes of midday sun in spring or summer to produce a sufficient amount. In winter, with less skin exposed and weaker sunlight, the same person would need close to two hours.
Geography shifts these numbers dramatically. In Miami during summer, just 3 minutes of midday sun can be enough. In Boston during winter, with heavy clothing limiting exposed skin to about 5 percent of the body, you’d need over two hours. Children with darker skin need even longer than these estimates. Because of all these variables, dietary intake and supplements are considered the more reliable way to ensure kids meet their daily target.
Food Sources of Vitamin D
Very few foods naturally contain significant vitamin D. Fatty fish like salmon and mackerel are the richest natural sources, with a 3-ounce serving of cooked salmon providing around 400 to 600 IU depending on the type. Beyond fish, most of the vitamin D in a child’s diet comes from fortified foods. A cup of fortified cow’s milk contains about 120 IU, so a child would need to drink roughly five cups a day to reach 600 IU from milk alone. Fortified orange juice provides a similar amount per cup. Some cereals and yogurts are also fortified, though the amounts vary by brand.
Egg yolks contain a small amount of vitamin D, typically around 40 IU per yolk. Cheese and butter contribute even less. For many children, especially picky eaters or those avoiding dairy, food alone won’t bridge the gap, which is why pediatricians often recommend a daily supplement.
Upper Limits and Safety
Vitamin D is fat-soluble, meaning excess amounts are stored in body fat rather than flushed out in urine. This makes toxicity possible if a child takes far more than recommended over a sustained period. The European Food Safety Authority sets the tolerable upper intake level at 50 mcg (2,000 IU) per day for children ages 1 to 10, and 100 mcg (4,000 IU) per day for adolescents aged 11 and older. For infants, the upper limit is generally set at 1,000 to 1,500 IU depending on the source.
Toxicity from vitamin D causes the body to absorb too much calcium, which can lead to nausea, vomiting, weakness, and in severe cases, kidney damage. It’s essentially impossible to get toxic amounts from food or sun exposure alone. The risk comes from supplement misuse, particularly when caregivers accidentally give adult-strength drops to an infant or double up on multiple vitamin D-containing supplements.
How Deficiency Is Diagnosed
If your child’s doctor suspects low vitamin D, they’ll order a blood test measuring 25-hydroxyvitamin D, the form that best reflects the body’s overall stores. The reference ranges used by most labs, based on guidance from the Institute of Medicine, are:
- Below 10 ng/mL: Severe deficiency
- 10 to 19 ng/mL: Mild to moderate deficiency
- 20 to 50 ng/mL: Optimal range
- 51 to 80 ng/mL: Increased risk of excess calcium in urine
- Above 80 ng/mL: Toxicity possible
These thresholds apply to children and adults alike. Routine screening isn’t recommended for all kids, but testing makes sense for children with risk factors like chronic illness, very limited sun exposure, or symptoms such as unexplained bone pain or muscle weakness.